LE3 .A278 2021

2021

Spooner, Ian
Mallory, Mark

Acadia University

Master of Science

Masters

Environmental Science

Environmental & Sustainability Studies

The impacts of landscape disruption and watercourse manipulation on productivity in an upland hydroelectric reservoir, Gaspereau Lake, in Nova Scotia were investigated using lake sediment and historical records. Alewife (Alosa pseudoharengus) are an anadromous species that are a significant biomass contributor in Gaspereau Lake, the effect of watershed disturbance on their contribution to lake productivity was also investigated. An influx of C and N accompanied by a subtle increase in chlorophyll a in the early 1900s corresponded to watershed and water level disturbance caused by logging. A productivity response to hydroelectric development and damming occurred considerably after these activities, increasing chlorophyll a accompanied by declining δ13C likely indicate the release of oxidation of the soil organic matter associated with lake level rise. Assessing the contribution of alewife to productivity in Gaspereau Lake is complicated by a fragmented historical record of visitation as well as the naturally mesotrophic conditions. The lake sediment geochemical record from a nearby reference lake, Black River Lake, that receives no alewife was used as a comparator. Alewife preferentially accumulate Sr during marine residency, allowing the utility of Sr to be assessed as a geochemical indicator of alewife residency. Higher Sr concentrations and a sharp decline in Sr associated with hydroelectric development in Gaspereau Lake compared to Black River Lake indicate that Sr may vary with alewife residency. The inverse relationship of Sr to Ti concentrations may also reflect a biogenic source for much of the Sr preserved in the Gaspereau Lake sediment core. The results of this study have shown that the lake sediment bulk geochemical record in both Gaspereau Lake and Black River Lake records the timing and magnitude of productivity and landscape stability changes associated with logging and hydroelectric development from the late 1800s until Present. However, the variability in these records indicates that unique reaction of seemingly similar environments. This research also emphasizes the complexity of decoupling indicators of autochthonous and allochthonous productivity when integrating nutrient influx from external vectors such as alewife..

The author retains copyright in this thesis. Any substantial copying or any other actions that exceed fair dealing or other exceptions in the Copyright Act require the permission of the author.

https://scholar.acadiau.ca/islandora/object/theses:3642